Image processing apparatus have been widely used in a variety of different applications. Such applications include, but are not limited to, printing, facsimile transmission/reception, medical imaging, video transmission/reception, and the like. In each instance, various ways of handling the data corresponding to the image have been devised. To this end, the image data may be encoded and/or decoded in accordance with one or more compression and/or decompression operations.
Entropy encoding/decoding may be used when lossless compression/decompression is needed. Different types of entropy encoding/decoding have been standardized for use in image processing apparatus. JBIG and JBIG2 are industry standards that are in common use. JBIG employs a form of entropy encoding/decoding known as arithmetic encoding/decoding. Compression methods that use arithmetic coding start by determining a model of the data. The model constitutes a prediction of what patterns will be found in pixels forming the image. Sophisticated models may be used in the arithmetic coding process. In these sophisticated models, higher-order modeling may be employed. In accordance with this higher-order modeling, the model used for the currently targeted pixel changes its estimation of the current probability of a pixel based on one or more pixels that precede it. The various pixels that are used to change the model for use in predicting the value of the target pixel is known as a context. Similarly, a context is generated and used in the decoding of a target pixel.
Image processing systems that employ a context for encoding and/or decoding image data may include memory storage that is specifically dedicated to storing context data. The context memory storage is cleared to an initial state upon completion of the encoding and/or decoding operations in preparation for processing a subsequent image. Clearing of the context memory is typically executed by a central processing unit that controls the whole apparatus. Alternatively, a codec may begin initializing the context memory storage after a command to process an image is received but before the codec begins actual processing of the image data. As such, the clearing of the context memory substantially increases the latency of the processing executed by the whole apparatus. As the throughput demands on image processing apparatus increase, new approaches to decreasing the latency of the image processing apparatus are desirable.